Vulcanisaeta distributa gen. nov., sp nov., and Vulcanisaeta souniana sp nov., novel hyperthermophilic rod-shaped crenarchaeotes isolated from hot springs in Japan

Seventeen strains of rod-shaped, heterotrophic, anaerobic, hyperthermophilic crenarchaeotes were isolated from several hot spring areas in eastern Japan, and eight representative strains were characterized further. Cells of these strains were straight to slightly curved rods, 0.4-0.6 gm in width. Occasionally, cells were branched or bore spherical bodies at the poles. They grew optimally at 85-90 degreesC and at pH 4.0-4.5. They utilized yeast extract, peptone, beef extract, Casamino acids, gelatin, starch, maltose and malate as carbon sources and sulfur and thiosulfate as possible electron acceptors. The DNA G+C contents of the novel isolates were 43.9-46.2 mol%. The lipids were mainly cyclic and acyclic tetraether core lipids. Phylogenetic analysis of the 16S rDNA sequences revealed that they represented an independent lineage in the family Thermoproteaceae. Moreover, comparison of the 16S rDNA sequences and a DNA-DNA hybridization study showed that they comprised two species, which could also be differentiated by the maximal growth temperature and degrees of NaCl tolerance. Therefore, a new genus, Vulcanisaeta gen. nov., in the family Thermoproteaceae is proposed to accommodate two novel species, Vulcanisaeta distributa sp. nov. and Vulcanisaeta souniana sp. nov. The type species is V. distributa and the type strains are V. distributa IC-017(T) (= JCM 11212(T) = DSM 14429(T)) and V. souniana IC-059(T) (= JCM 11219(T) = DSM 14430(T)).